This invention relates to a method of supplying record mediums such as single sheets or continuous papers as rolled papers or fanfold papers on which images are formed by means of an electrophotograph output device, and more particularly to a record medium supply method for electrophotographing, which is capable of saving record medium and mitigating wear of a photosensitive member in an electrophotograph output device to contribute to prolongation of life time of the output device.
Further, this invention also relates to an apparatus for carrying out the above described method.
Printers of the electrophotography in combination of copying technique and optical techniques have various advantages such as high speed printing, high grade printed characters, low noise and the like and have been widely utilized as new information output devices.
FIG. 1 schematically illustrates an example of the arrangement of such a printer viewed in a direction in parallel with a rotating axis of a photosensitive drum used in the printer.
This printer comprises a photosensitive drum 11 rotatable in a predetermined direction, an electric charger 13 for charging the photosensitive drum, means (not shown) for generating laser beams 15 scanning a surface of the photosensitive drum 11 in the direction of its rotating axis, and a developing unit 17. These members are arranged in succession along a rotating direction of the photosensitive drum 11. The laser beams 15 are irradiated selectively on the basis of image data onto the photosensitive drum 11 charged to -400 to 500 V by the electric charger 13 to form electrostatic latent images concerning with images on the surface of the photosensitive drum. The electrostatic latent images are then made sensible by toner supplied from the developing unit 17.
On the other hand, a record medium 19 is supplied at a position which is in opposition to and spaced apart from the photosensitive drum 11 by a suitable distance downstream of the developing unit 17 in the rotating direction of the drum 11. In this embodiment, the record medium 19 is a part of a rolled paper 19a housed in position in the printer housing 10. The record medium 19 paid out from the rolled paper 19a extends about a tension roller 21 and a stationary roller 23 and passes in opposition to the photosensitive drum 11. Thereafter the record medium 19 continuously passes about a paper feeding roller 25 and between a back-up roller 27 and a heat roller 29 and arrives at a paper feeding roller 31.
Moreover, the printer comprises a transfer charger 33 at a location where the record medium 19 is in opposition to the photosensitive drum 11 and on an opposite (rear) side of the record medium 19 facing to the photosensitive drum 11.
The sensible images which have been converted from the electrostatic latent images by the developing unit 17 are fed to the location where they are opposed to the record medium as the photosensitive drum 11 rotates. The toner on the electrostatic latent images is transferred to a transferring zone of the record medium by means of a transfer charger 33 provided on the back side of the record medium 19. In other words, the transferring position is the location where the transfer charger 33 is provided.
The zone of the record medium 19 on which the toner is transferred is then fed into a clearance between the back-up roller 27 and the heat roller 29 by means of the paper feeding rollers 25 and 31. The toner is printed to the zone of the record medium 19 by the heat roller 29 to form images on the record medium 19. Then, a new record medium is supplied from the roller paper 19a by means of the paper feeding roller 25 and 31.
On the other hand, the part of the photosensitive drum which has completed the transfer of the images is brought into opposition to a cleaning unit 35 with the rotation of the photosensitive drum 11 to cause the part of the drum to be discharged and cleaned.
With the printer as above described, the above operations are cyclically effected relative to the photosensitive drum 11, and new transfer zones of the record medium 19 are successively fed from the rolled paper 19a so as to oppose the photosensitive drum in synchronism with the rotation of the photosensitive drum 11.
In the method of supplying the record medium in synchronism with the rotation of the photosensitive drum according to the prior art, following problems arise with start of the printer or in forming images after the printer is kept unused for a long period of time.
In order to form electrostatic latent images concerning required images on the surface of the photosensitive drum 11 and to convert the latent images into sensible ones by toner which is then transferred to the record medium, it is needed to carry out the respective treatment, such as charging, selective light irradiation, development and transfer in succession with respect to the photosensitive drum 11 as above described. Therefore, there is no toner concerning the images at the transfer position immediately after the image formation is started. Under such a condition, if the record medium is supplied in synchronism with the rotation of the photosensitive drum, an image is not formed on part of the record medium which has been fed during moving of the first electrostatic latent images converted into visible ones to the transfer position. During such a period, the record medium is superfluously consumed.
In a printer (output device) according to the electrophotography, moreover, the part of the photosensitive drum which is charged and irradiated by light beams forms electrostatic latent images to which the toner clings in the reversal development system. In this case, at the commencement of the formation of the images, the part of the photosensitive drum 11 upstream of the electric charger 13 will be brought into opposition to the record medium without being charged. Since the toner of the developing unit 17 clings to the part of the photosensitive drum which is not charged and at zero voltage electric potential, the toner would cling to the record medium. However, the clung toner does not concern with the required images and serves only to foul the record medium which will be wasted.
In case of using a fanfold paper as the record medium, the following problem arises in addition to the above problem.
As well known, the fanfold paper is a continuous long paper formed with feeding apertures in both edges and with intermittent slit lines for folding along width directions of the paper with a predetermined interval in a longitudinal direction of the paper Instead of the paper feeding roller, by using a known tractor having pawls to be engaged with the feeding apertures of the fanfold paper, a formation of images on the fanfold paper can be effected with the printer explained in reference with FIG. 1 in the same manner as using the rolled paper. The printed fanfold paper is then separated into single sheet.
In case that such a fanfold paper is used as a record medium, the printing by a printer is usually effected on printable parts between intermittent slit lines of the fanfold paper. Therefore, the printer stops the output of data when the intermittent slit line arrives at the proximity of the transfer position until the slit line has passed the transfer position and a leading portion of a next printable part of the paper has arrived thereat. Moreover, the feeding of the fanfold paper is temporarily stopped by a mechanism (tractor) for feeding the fanfold paper, when the next printable part of the paper has arrived at the transfer position, and after a while the mechanism is again started to feed the paper when images on the photosensitive drum have arrived at the transfer position which correspond to again started output data.
Therefore, the fanfold paper is stopped while it is in contact with the rotating photosensitive drum so that a frictional force is caused between the paper and the drum and gives rise to wear of the drum.